In the operation of gas turbines, particularly in electric power plants, various kinds of control systems have been employed from relay-pneumatic type systems, to analog type electronic controls, to digital controls, and more recently to computer based software controls. U.S. Pat. No. 4,308,463 - Giras et al., assigned to the assignee of the present invention and incorporated herein by reference, lists several of such prior systems. That patent particularly discloses a digital computer based control system for use with gas turbine electric power plants. It will be noted that the Giras et al. patent is one of a family of patents all of which are cross referenced therein.
Subsequent to the Giras et al. patent, other control systems have been introduced by Westinghouse Electric Corporation of Pittsburgh, Pennsylvania under the designations POWERLOGIC and POWERLOGIC II. Similar to the Giras et al. patent these control systems are used to control gas turbine electric power plants. However, such control systems are primarily micro-processor based computer systems, i.e. the control systems are implemented in software, whereas prior control systems were implemented in electrical and electronic hardware.
The operating philosophy behind the POWERLOGIC and POWERLOGIC II control system is that it shall be possible for the operator to bring the turbine generator from a so-called ready-start condition to full power by depressing a single button. All modes of turbine-generator operation are to be controlled. For example, ignition control in prior combustion turbines, such as the W501D5, utilize compressor discharge pressure and other factors as a measure for determining when ignition should occur. Unfortunately, monitoring such factors can still result in a failure for ignition to occur. For example, ambient temperature can effect air flow through a combustion turbine by as much as 6 percent. The possibility exists that certain fuel/air conditions which are outside the ignition envelope of the combustion turbine could occur. If ignition failure occurs there is presently no quick way to determine what went wrong. Consequently, a need exists for more reliably diagnosing ignition failures.
Although, the operation of a gas turbine electric power plant and the POWERLOGIC II control system are described generally herein, it should be noted that the invention is particularly concerned with diagnosing the ignition process in gas turbines.